26. Amines

Within each structure, rank the indicated nitrogens by increasing basicity.

(a)

(b)

Rank each set of compounds in order of increasing basicity.

(b) aniline, p-methylaniline, p-nitroaniline

Show how you would convert alanine to the following derivatives. Show the structure of the product in each case.

(c) N-benzyloxycarbonyl alanine

(d) tert-butyloxycarbonyl alanine

Dimethylamine, (CH₃)₂NH, has a molecular weight of 45 and a boiling point of 7.4 °C. Trimethylamine, (CH₃)₃N, has a higher molecular weight (59) but a lower boiling point (3.5 °C). Explain this apparent discrepancy.

Predict the products of the following reactions:

(a) excess NH₃ + Ph–CH₂CH₂CH₂Br →

Two widely used pain relievers are aspirin and acetaminophen. Show how you would synthesize these drugs from phenol.

Propose a mechanism to show the individual alkylations that form this quaternary ammonium salt.

Rank the amines in each set in order of increasing basicity.

(e)

The ribonucleosides that make up ribonucleic acid (RNA) are composed of D-ribose (a sugar) and four heterocyclic “bases.” The general structure of a ribonucleoside is shown here.

The four heterocyclic bases are cytosine, uracil, guanine, and adenine. Cytosine and uracil are called pyrimidine bases because their structures resemble pyrimidine. Guanine and adenine are called purine bases because their structures resemble purine.

b. Predict which nitrogen atoms are basic.

Basicity depends on availability of an electron pair to bond a proton. Correlate structural effects in these amines with their basicities.

(a) Explain this order:

Rank each set of compounds in order of increasing basicity.

(c) aniline, pyrrole, pyridine, piperidine

Which of the amines listed next is resolved into enantiomers? In each case, explain why interconversion of the enantiomers does or does not take place.

(a) cis-2-methylcyclohexanamine 

(b) N-ethyl-N-methylcyclohexanamine 

(c) N-methylaziridine 

(d) ethylmethylanilinium iodide

(e) methylethylpropylisopropylammoniumiodide

Rank the amines in each set in order of increasing basicity.

(a)

Within each structure, rank the indicated nitrogens by increasing basicity.

(d)

(e)

Basicity depends on availability of an electron pair to bond a proton. Correlate structural effects in these amines with their basicities.

(b) Explain: